Temperature and level sensor with heater and heat transfer means



July 4, 1967 p NQVAS ET AL 3,329,787

TEMPERATURE AND LEVELv SENSOR WITH HEATER AND HEAT TRANSFER MEANS Filed Aug. 2, 1965 fnuehfars. peferfiA/ouaa I 12066 ZflZYrrwi, \fy [mum M1 United States Patent 3,329,787 TEMPERATURE AND LEVEL SENSOR WITH HEATER AND HEAT TRANSFER MEANS Peter P. Novas and Robert D. Ernst, Prospect Heights,

11]., assignors to Napor Corporation, Chicago, Ill., a

corporation of Delaware Filed Aug. 2, 1965, Ser. No. 476,341 3 Claims. (Cl. 200-122) Our present invention relates to a temperature and level sensor adapted for use as an electrical circuit controller in association with machinery and the like.

In machinery having relatively movable parts, and particularly in heavy duty or high speed machinery, 1t is necessary to reduce friction between the bearing surfaces in relative motion. The required reduction in friction is usually accomplished through the provision of a coolant or lubricant. In such case, when there is a malfunction 1n the machinery causing either overheating or loss of the coolant or lubricant, serious damage can occur to the machinery due to the resultant overheating of the relatively movable parts.

It is an object of our present invention to provide a temperature and level sensor for detecting or anticipating overheating of rotating, rubbing, or other movable, parts in machinery due to overheating or loss of coolant or lubricant.

It is another object of our present invention to provide a temperature and level sensor, as described, which is operable to close an electrical control circuit upon overheating or loss of the coolant or lubricant. In this connection, we provide a temperature responsive mercury switch, which is mounted in a housing projecting into the coolant or lubricant of the machinery, and which serves to close an electrical control circuit either when the temperature of the fluid medium exceeds the normal operating temperature by a predetermined amount or when the level of the coolant or lubricant drops below that of the mercury switch.

As a feature of our present invention, we associate with the mercury switch a heater coil for generating a predetermined amount of heat which is greater than the heat of the fluid medium at normal operating temperature. In normal operation, part of the coil heat in excess of the heat of the fluid medium is dissipated into the fluid medium, while the other part of the excess coil heat is directed to the mercury switch. The latter increment of heat, together with the heat of the fluid medium at normal operating temperature, is insufficient to close the mercury switch. However, when there is a loss of coolant or lubricant about the housing and hence an absence of fluid medium into which heat generated by the heater coil would otherwise be partially dissipated, the total heat generated by the heater coil is directed to the mercury switch for effecting closing of the latter.

It is a further feature of our present invention that, except for applied voltage, the electrical circuit controller is independent of any amplifying devices for providing a' signal of suflicient magnitude to activate current available signal or control devices connected in the control circuit.

Now in order to acquaint those skilled in the art with the manner of constructing and using temperature and level sensors in accordance with the principles of our present invention, we shall describe in connection with the accompanying drawing a preferred embodiment of our invention.

In the drawing:

FIGURE 1 is a side elevational view of the tempera ture and level sensor of our present invention extending through the wall of a sump or tank, a fragmentary portion of which is shown in section;

FIGURE 2 is a lengthwise median sectional view of the temperature and level sensor of FIGURE 1;

FIGURE 3 is an end elevational view of the temperature and level sensor of FIGURE 1;

FIGURE 4 is a transverse sectional view, taken substantially along the line 44 in FIGURE 2, looking in the direction indicated by the arrows; and

FIGURE 5 is a schematical wiring diagram of a circuit incorporating the temperature and level sensor of our present invention.

Referring now to the drawing, there is indicated generally by the reference numeral 10 the temperature and level sensor or electrical circuit controller of our present invention. The controller 10 comprises a generally tubular elongated housing 12 having a closed end 14 and an intermediate threaded portion 16. The unit 10 is adapted to be threaded into the wall of a sump or tank 18 associatedwith or forming part of machinery. The housing 12 is thereby arranged to project into the fluid medium (not shown), such as coolant or lubricant, within the sump 18. Mounted lengthwise in the housing 12 is a temperature responsive mercury switch 20 which includes a glass casing 22, an integral reservoir bulb 24 and capillary tube 26 within the casing 22, and a pair of spaced contacts 28 and 30 preferably comprised of platinum wires extending through the capillary tube 26. The reservoir bulb 24 is filled with mercury 32 which is expandable within the capillary tube 26 in response to temperature changes. In addition, terminal bands 34 and 36 may be arranged about the casing 22 for a purpose to be described hereinafter.

Disposed within the housing 12 adjacent the closed end 14 there is a heater coil assembly 38 which includes a core or spool 40 recessed to receive the end of casing 22, and a coil 42. Arranged intermediate of the housing 12 and the casing 22 adjacent and in line with the reservoir bulb 24 are a pair of arcuate metal heat transfer bands 44 which may be fabricated of good heat conducting material, for example, of beryllium copper. In addition to serving as heat transfer paths between the housing or casing 12 and the glass casing 22 of the mercury switch 20, the bands 44 substantially center the glass casing 22 within the housing 12, and resiliently support the glass casing 22 thereby protecting it against undue vibration. An insulating washer 46 is disposed at the ends of the heat transfer bands 44 adjacent the heater coil assembly 38 to prevent direct heat transfer from the heater to the bands and necessitating transfer of heat to the bands from the coil through the casing and/or fluid medium in which the sensor is positioned, and a centering washer 48 of heat insulating material is mounted at the other ends of the heat transfer bands 44. Mounted in the end of the housing 12 exteriorly of the sump 18 is a terminal bushing 50 providing support for a pair of terminal prongs 52 and 54. The interior of the housing 12 about the contact end of the switch and between the assembly 38 and the glass casing 22 is filled with a suitable resilient, heat insulating potting compound 56.

As shown in FIGURE 5, the one side of the heater coil 42 and the terminal prong 52 are interconnected at the terminal band 34, the other side of the heater coil 42 and the contact 28 are interconnected at the terminal band 36, the contact 28 is grounded to the housing 12, and the contact 30 has connection with the terminal prong 54. The terminal prong 52 and the casing 12 are adapted to be connected to a source of power for actuating the heater coil 42, while the terminal prong 54 is adapted to be connected to an emergency signal or control device not shown.

The elements of the controller 10 are so arranged that the normal operating temperature of the fluid medium, either coolant or lubricant, in the sump 18 causes the mercury 32 to expand within the capillary tube 26 to a point adjacent the contact 28. In addition, the heater coil 42 when energized generates a predetermined amount of heat which is greater than the heat of the fluid medium at normal operating temperature. Normally, part of the coil heat in excess of the heat of the fluid medium is directed to the mercury 32 to expand the same within the capillary tube 26 beyond the point corresponding to the normal operating temperature of the fluid medium to a point intermediate the contacts 28 and 30; the other part of the excess coil heat is dissipated through the housing 12 into the adjacent fluid medium. The total amount of heat generated by the coil 42 is determined by the size of the coil and the amount of current applied thereto.

Now when the temperature of the fluid medium within the sump .18 rises above the normal operating temperature, due to malfunctioning of the machinery or otherwise, the mercury 32 is caused to expand still further within the capillary tube 26 until, in response to a predetermined temperature rise of the fluid medium, the mercury bridges the contacts 28 and 30 causing energization of the control device connected to the terminal prong 54. Also, if there should be a loss of fluid medium in the sump 18 causing the level of the fluid medium to drop below that of the unit 10, heat generated by the heater coil 42 is no longer partially dissipated through the housing 12 into the fluid medium. In such circumstances, all of the heat generated by the coil 42 is transferred through the casing 12 and the heat transfer bands 44 to the reservoir bulb 24 causing the mercury 32 to expand within the capillary tube 26 to bridge the contacts 28 and 30 and provide a closed circuit for the control device. It will thus be apparent that we have provided a temperature and level responsive electrical circuit controller, in a single unit, for sensing overheating or loss of coolant or lubricant to detect or anticipate overheating of the relatively movable parts of machinery in order to prevent damage to the latter.

By way of illustration and not limitation, if the normal operating temperature of the fluid medium in the sump 18 is 200 F., the contact 28 may be located at the mercury expansion point corresponding to 200 F. while the contact 30 may be located at the mercury expansion point corresponding to 260 F. At these temperature settings, a heater coil 42 is provided that will, when fluid medium is present at normal operating temperature, furnish a small increment of additional heat to expand the mercury 32 to a point corresponding approximately to 230 F., midway between the contacts 28 and 30, and upon a loss of fluid medium about the unit 10, furnish sufficient heat to expand the mercury to the contact 30. Under these conditions, upon either overheating of the fluid medium by 30 F. to 230 F or loss of fluid medium, the contacts 28 and 30 are bridged by the mercury 32 for closing the control circuit. Of course, it will be appreciated that the temperature and level sensor of our present invention can be readily adjusted to accommodate numerous temperature settings and differentials for a wide range of level and temperature control applications. Finally, it will also be appreciated that our temperature and level sensor is capable of activating directly (through solidstate or electro-mechanical means) an unlimited variety of signal or control devices for visual, audible, electrical, mechanical and electro-mechanical indication or control.

While we have shown and described what we believe to be a preferred embodiment of our present invention, it will be understood by those skilled in the art that various rearrangements and modifications may be made therein without departing from the spirit and scope of our invention.

We claim:

1. A temperature and level sensor comprising, an elongated tubular casing adapted to extend into a container of fluid medium to sense the temperature and level of said medium, said casing being closed at the free end thereof Within said medium, a temperature responsive mercury switch within said casing including an elongated glass body, a reservoir in said body in communication with a capillary tube therein, mercury in said reservoir expandable in said tube, first and second spaced contacts along said tube adapted to be connected to electrical circuitry whereby predetermined temperature expansion of said mercury causes electrical connection of said contacts, heater means within and in direct contact with said casing at the free end thereof, resilient heat insulating means between said heater means and glass body, heat transfer means within said casing between said casing and glass body for creating a heat path therebetween and aligned with said reservoir, heat insulating means Within said casing between the casing and glass body and between said heater means and the adjacent end of the heat transfer means, and said heater means having such capacity that it will cause expansion of the mercury to electrically interconnect the contacts in the event the temperature of the medium exceeds a predetermined amount or the medium level drops below a predetermined level.

2. A temperature and level sensor as defined in claim 1, wherein said heat transfer means resiliently supports said switch substantially centrally within said casing.

3. A temperature and level sensor as defined in claim 1, and second heat insulating means within said casing between the casing and glass body and at the end of said heat transfer means remote from the end thereof adjacent the first mentioned heat insulating means.

References Cited UNITED STATES PATENTS 1,560,119 11/1925 Stoekle 200122 2,158,146 5/1939 Parks et al. 200-122 2,619,566 11/1952 Mahoney 200-122 3,102,179 8/ 1963 Hermeyer 200-122 BERNARD A. GILHEANY, Primary Examiner.

H. A. LEWITTER, Assistant Examiner. 

1. A TEMPERATURE AND LEVEL SENSOR COMPRISING, AN ELONGATED TUBULAR CASING ADAPTED TO EXTEND INTO A CONTAINER OF FLUID MEDIUM TO SENSE THE TEMPERATURE AND LEVEL OF SAID MEDIUM, SAID CASING BEING CLOSED AT THE FREE END THEREOF WITHIN SAID MEDIUM, A TEMPERATURE RESPONSIVE MERCURY SWITCH WITHIN SAID CASING INCLUDING AN ELONGATED GLASS BODY, A RESERVOIR IN SAID BODY IN COMMUNICATION WITH A CAPILLARY TUBE THEREIN, MERCURY IN SAID RESERVOIR EXPANDABLE IN SAID TUBE, FIRST AND SECOND SPACED CONTACTS ALONG SAID TUBE ADAPTED TO BE CONNECTED TO ELECTRICAL CIRCUITRY WHEREBY PREDETERMINED TEMPERATURE EXPANSION OF SAID MERCURY CAUSES ELECTRICAL CONNECTION OF SAID CONTACTS, HEATER MEANS WITHIN AND IN DIRECT CONTACT WITH SAID CASING AT THE FREE END THEREOF, RESILIENT HEAT INSULATING MEANS BETWEEN SAID HEATER MEANS AND GLASS BODY, HEAT TRANSFER MEANS WITHIN SAID CASING BETWEEN SAID CASING AND GLASS BODY FOR CREATING A HEAT PATH THEREBETWEEN AND ALIGNED WITH SAID RESERVOIR, HEAT INSULATING MEANS WITHIN SAID 